Drug abusers with severe mental and emotional disturbances constitute a heterogeneous group that has become increasingly important in clinical practice and psychiatric research. Clinicians who treat such patients are often faced with the difficult problem of distinguishing between drug abusers who are primarily reacting to drugs and those who have a major psychiatric illness. Although a number of studies have documented the extensiveness of the problem, relatively little is known about potentially useful differential factors such as long-term course and family history. We are proposing a personal interview follow-up study of drug abusers with psychosis in order to investigate differential course and outcome in this heterogeneous group of patients. We also wish to gather family history data from these personal interviews with probands. The primary goal is to develop preliminary criteria for identifying drug abusers who have a major psychiatric illness such as schizophrenia. Secondary analyses will examine homogeneous subgroups within this major diagnostic grouping. From pilot research we have identified several potentially useful factors for differential diagnosis--clinical features, duration of symptoms, premorbid personality, and family history of psychiatric illness. The results of a preliminary telephone interview follow-up study have demonstrated the feasibility of following up drug abusers with psychosis (DAP). To accomplish our objectives, we will conduct a historical follow-up study of a) a cohort of 72 drug abusers hospitalized with psychosis in 1971-72, and b) comparison cohorts of drug abusers without psychosis (n=30) and non drug-abusing patients with schizophrenia (n=46) or atypical schizophrenia (n=28). Psychiatric course and outcome will be determined from medical and vital records and from blind structured psychiatric interviews with all consenting index patients. These interviews will also involve the collection of family history information. The proposed research will generate follow-up and family data for analyses of differential factors which may discriminate between drug abusers with psychosis and other psychiatric patients and between subtypes of drug abusers with psychosis. The proposed research will also provide practical knowledge necessary in planning a large-scale follow-up and family study of DAP.